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Yeah. I still don't quite understand the purpose of it. Is it to discourage delegating your Steem to others?

It is to prevent double voting with the same SP. The cooldown period is equal to the rewards pool window, making it impossible to upvote your post, delegate to a second account and then upvote the same post with the same SP :)

Ah...yes. That does make sense. 👍

Yep. Mostly so you don't delegate, then undelegate continuously.